The overall goal of this proposal is to understand further the functions of HSV-1 Alpha-polypeptide, ICP-4, during cytolytic infection. HSV ICP-4 regulates positively the appearance of HSV Beta-polypeptides which are necessary for viral replication during productive infection. The focus of this proposal is to ascertain whether ICP-4 may act as a determinant HSV pathogenesis by modulating the expression of specific cellular genes. Cellular genes whose expression is regulated by HSV ICP-4 activity during cytolytic infection will be defined, isolated, and characterized by molecular hybridization and cDNA cloning techniques. Determination of the specificity with which ICP-4 exerts regulation on cell gene expression will be achieved by assaying cell transcripts of candidate cell cDNA clones following infection of cells with a panel of ts mutants for ICP-4. Identification of isolated cDNA clones will afforded by DNA sequence analysis followed by comparison with DNA sequences for known eukaryotic genes provided in the Los Alamos Databank. Trans and/or cis mechanisms of ICP-4 regulation of candidate cellular genes will be evaluated by transient expression assays following transfection of mammalian expression vectors containing combinations of ICP-4, HSV TK, and various portions of candidate genomic cell genes into appropriate host cells. Results from these successive series of experiments will define more definitively the multifunctional roles of HSV-1 ICP-4 in viral pathogenesis.